PFC^3D-BASED NUMERICAL SIMULATION ANALYSIS METHOD FOR MOTION CHARACTERISTICS OF ROCKFALL

Rockfall disasters frequently occur in mountainous regions,and efficiently and accurately predicting their motion characteristics—such as trajectory,motion form,velocity,and energy—is essential for slope disaster prevention and control. Existing studies mostly use a single slope material and rigid spherical rockfall models,which struggle to capture realistic rockfall behavior. In this study,a 3D slope modeling process based on actual terrain data was first described. Rigid and fragmentable discrete element models of rockfalls with four different shapes(regular hexahedron,regular dodecahedron,regular icosahedron,and sphere)were then established,along with a slope rockfall motion analysis model,using the PFC^3D software. Based on field rockfall impact tests and uniaxial/triaxial compression tests on rocks,the parameters of the linear contact model(representing rockfall-slope interaction for smooth bedrock,debris accumulation layers,and loose gravelly soil)and the parallel bond contact model(characterizing inter-particle interaction within rockfalls for red sandstone,granite,and rock-like material)were calibrated and validated. The influences of rockfall shape,size,and slope material on motion characteristics were analyzed. The results indicate that as rockfall size increases and sphericity decreases,energy loss increases,leading to lower peak translational and rotational velocities during motion. Lower slope material hardness results in larger impact and friction contact areas,causing greater energy loss and reduced peak translational and rotational velocities. Rockfall fragmentation should be considered when the slope material is hard and the rockfall is weak,whereas rockfall can be treated as a rigid body when the slope material is soft. Finally,a rockfall disaster in Miaoli County,Taiwan Province,China,was numerically reproduced. The simulation verified that the established fragmentable rockfall model and the proposed numerical analysis method can accurately predict fragment characteristics,motion trajectories,and deposition positions in actual rockfall events,providing a valuable reference for rockfall protection design in mountainous regions.